Uterine contractions are intermittent and co-ordinated tightenings of the uterine muscle. Uterine contractions provide the force that makes labour progress, by causing the baby to descend through the birth canal and making the cervix efface (shorten), and dilate (open). This force is related to the frequency, strength and duration of the contractions. Oxytocin is a natural hormone that causes uterine contractions. A synthetic version of oxytocin is often administered during labour to increase the frequency, duration and strength of uterine contractions or to induce labour. The medication is administered through a continuous intravenous infusion. There is no fixed dosage as in antibiotic therapy; rather the dose is adjusted frequently according to the patient's response to achieve the desired frequency and intensity of contractions.
When the uterine muscle contracts, the maternal blood vessels in it are constricted causing a temporary reduction in the blood flow and delivery of oxygen to the baby's placenta. Relaxation of the contraction restores the flow and oxygen delivery to the baby. In normal circumstances, babies tolerate contractions well. However, in other circumstances, such as when the placenta malfunctions or the contractions are excessively frequent with little or no relaxation time between them, the baby may not tolerate this reduction in oxygen delivery. If the situation remains uncorrected or worsens it may result in injury to the baby's brain and permanent disability.
At present, clinical staff estimates the frequency of contractions by feeling the mother's abdomen for a few minutes and noting the timing of a few contractions or by examining a paper tracing that shows a recording of contraction pressures/intensity over time. These assessments are performed periodically and the results recorded in the medical record.
A deficiency with the above-described methods for assessing contraction frequency is that they are prone to inaccuracy and incompleteness because they are visual estimates based on short selected segments of the tracing and the caregiver may fail to make assessments at the prescribed time intervals and may fail to appreciate the degree and duration of the abnormality as well as the response of the baby. Thus, there can be a delay or failure to recognize overly frequent contractions, to adjust the medication correctly, resulting in an iatrogenic injury to the baby.
In the context of the above, there is a need to provide a method and device for monitoring contractions for an obstetrics patient that alleviates at least in part problems associated with the existing methods and devices.